'Upper' and 'lower' abs aren't separate muscles

It's one rectus abdominis, not two muscles you can train independently

Fitness culture has long split the abs into 'upper' and 'lower,' with dedicated exercises for each. Anatomically that's not quite right: the rectus abdominis is one long muscle running from the ribs to the pelvis, divided into segments by tendinous bands (that's where the visible 'six-pack' comes from) — not into functionally independent upper and lower halves.

EMG studies show that exercises considered 'upper-ab' (like crunches) and 'lower-ab' (like leg raises) do shift activation slightly along the muscle — but the difference is a few percentage points, not a clean split into independent zones you can target one without the other.

A bigger factor in ab visibility isn't exercise selection at all — it's overall body-fat percentage. The rectus abdominis doesn't have a separate fat depot specifically 'up top' or 'down low' — fat distribution across the belly is driven by broader genetic and hormonal factors.